This is the second wave of a six-year panel study. The first wave consisted of 1400 people 65 and older living in the community, 400 living in institutions, and 800 of their helpers. It is designed to test out the hypothesis, Groups can optimally manage those services which have dimensions which match their structure. The assumption is made that services can be classified by the same dimensions as groups. Using this principle and data from the first wave, an attempt is made to predict which groups (spouses, relatives, friends, neighbors, or staff of institutions), can provide which services as older persons move from states of health and marriage to states of singlehood and illness, to institutionalization. These same principles enable one to elaborate on prior findings that people wth informal ties live longer by predicting which informal groups are most likely to lower mortality rates at time 2 for each state of health at time 1. The principle of matching is based on two parallel developments in organizational theory and primary group (support group) theory. Both fields started with the assumption that there was one ideal group for handling all services. They both concluded that no single group was ideal for all services. The organizational theorist developed different schemes for classifying services and structures. The primary theorist generally had no system for classifying services. The present formulation offers a general solution for both. As such, this study seeks to fill in two lacunae in the field of aging: (1) principles for determining which services each group can provide and (2) how this changes over the life cycle of older people (that is, starting with those 65 and older). In the second wave of this panel it is expected that the study will reinterview 990 older people, identify 630 as having died, and will find 180 untraceable or too ill to be reinterviewed.